1. Technical Field
This invention relates to a method and system for maintaining a storage system discovery record and a cluster bootstrap record in a cluster environment. More specifically, the invention relates to performing an update to the cluster bootstrap record in the event of a change in cluster membership, and recovery of the discovery record in the event of a disaster.
2. Description of the Prior Art
A cluster may be one node or, more commonly, a set of multiple nodes coordinating access to a set of shared storage subsystems typically through a storage area network. Each cluster will have one node that will function as a cluster leader to coordinate communication among nodes in the cluster. A cluster has cluster bootstrap information to enable nodes to join a cluster and to communicate across the cluster. Such information may include, cluster membership information, node identification information, node names, node identifiers, node IP addresses, as well as the last consistent state of a node in the cluster. In general, cluster bootstrap information is stored in a cluster bootstrap record by a cluster leader in a known location in the shared storage system.
Shared storage systems may come in various forms, including a storage area network and a back-end storage system. The shared storage includes a plurality of disks which may be accessible to each of the nodes in the cluster. The shared storage may be assigned to a single cluster or partitioned for multiple clusters. In a cluster environment, each node that is a member of the cluster has access to the shared storage media assigned to that cluster. If the shared storage is partitioned, then each node in the cluster will have access to the storage media assigned to the partition. One disk in the shared storage is generally designated as a master disk for the cluster. Within the cluster a discovery record is generally maintained in a known location on a local storage media for each node and is accessible by the associated node. The discovery record generally includes disk and cluster data, a unique installation identifier, and a unique cluster identifier. This information allows each node to discover at boot time, the set of shared disks owned by the cluster to which the node belongs, including the cluster's master disk. Accordingly, a discovery record within a cluster's master disk is maintained in order to identify the cluster and the master disk to each node in the cluster.
In certain of the current cluster environments, a copy of the discovery record and the cluster bootstrap record is stored on each node's local storage within the cluster. However, there are drawbacks associated with the prior art storage of discovery and bootstrap records on local storage. One problem is the resolution of inconsistent copies of the discovery and cluster bootstrap records as stored on each node's local storage in the cluster. In a disaster recovery situation, restoration of backup copies of each node's local copy of their discovery and bootstrap records is required. This remains necessary as each node's unique discovery and cluster bootstrap records are maintained exclusively on that node's local storage media and failure to restore the proper discovery and cluster bootstrap records to the proper node may effect the function of the node and cluster. Therefore, backup and restoration functions require the backup and restoration of each node's discovery and cluster bootstrap records in order to accomplish a complete backup and restoration of the cluster system. In certain other cluster environments, an IP multicast address may be used for cluster discovery by querying on a well known multicast address with all other nodes responding to that query. The problem with this approach is that IP multicasting has network limitations and does not solve the storage discovery problem. Accordingly, there are limitations associated with storage of consistent copies of the bootstrap record and discovery information across multiple nodes in a cluster, as well as with the IP multicast address approach.
There is therefore a need to make the backup and restore of discovery and cluster bootstrap records transparent across the cluster to facilitate recovery of data. There is a further need to eliminate issues arising from maintaining inconsistent discovery and cluster bootstrap records when restoring a cluster or a node within a cluster.